This collaborative effort is an extension of work supported by a grant funded for monkey studies (RO1 NS17413-20, 7/1/96 - 6/30/2001). It is conducted in a synergistic fashion together with similar and parallel experiments to be carried out with humans using. The general goal of this research is to understand the neural mechanisms underlying praxis, that is complex, purposeful motor actions; these mechanisms are largely unknown. In the monkey studies, rhesus monkeys are trained to perform tasks commonly used to determine the presence of constructional apraxia in brain-damaged human patients, including copying simple geometrical figures, assembling objects out of component parts, and route finding in a maze. The activity of single cells during task performance is recorded in key cortical areas of the monkey brain using a 7-microelectrode system. We have started examining in human subjects using fMRI at 4 Tesla which regions are activated during identical or analogous tasks. Extensive preliminary data has been collected demonstrating that activity is primarily in the frontal cortex, a finding that was unexpected.